1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP
  27 
  28 #include "classfile/javaClasses.hpp"
  29 #include "gc_implementation/g1/heapRegionSet.hpp"
  30 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  31 #include "gc_implementation/shared/gcId.hpp"
  32 #include "utilities/taskqueue.hpp"
  33 
  34 class G1CollectedHeap;
  35 class CMBitMap;
  36 class CMTask;
  37 typedef GenericTaskQueue<oop, mtGC>            CMTaskQueue;
  38 typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
  39 
  40 // Closure used by CM during concurrent reference discovery
  41 // and reference processing (during remarking) to determine
  42 // if a particular object is alive. It is primarily used
  43 // to determine if referents of discovered reference objects
  44 // are alive. An instance is also embedded into the
  45 // reference processor as the _is_alive_non_header field
  46 class G1CMIsAliveClosure: public BoolObjectClosure {
  47   G1CollectedHeap* _g1;
  48  public:
  49   G1CMIsAliveClosure() { }
  50   G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
  51 
  52   bool do_object_b(oop obj);
  53 };
  54 
  55 // A generic CM bit map.  This is essentially a wrapper around the BitMap
  56 // class, with one bit per (1<<_shifter) HeapWords.
  57 
  58 class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
  59  protected:
  60   HeapWord* _bmStartWord;      // base address of range covered by map
  61   size_t    _bmWordSize;       // map size (in #HeapWords covered)
  62   const int _shifter;          // map to char or bit
  63   BitMap    _bm;               // the bit map itself
  64 
  65  public:
  66   // constructor
  67   CMBitMapRO(int shifter);
  68 
  69   enum { do_yield = true };
  70 
  71   // inquiries
  72   HeapWord* startWord()   const { return _bmStartWord; }
  73   size_t    sizeInWords() const { return _bmWordSize;  }
  74   // the following is one past the last word in space
  75   HeapWord* endWord()     const { return _bmStartWord + _bmWordSize; }
  76 
  77   // read marks
  78 
  79   bool isMarked(HeapWord* addr) const {
  80     assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
  81            "outside underlying space?");
  82     return _bm.at(heapWordToOffset(addr));
  83   }
  84 
  85   // iteration
  86   inline bool iterate(BitMapClosure* cl, MemRegion mr);
  87   inline bool iterate(BitMapClosure* cl);
  88 
  89   // Return the address corresponding to the next marked bit at or after
  90   // "addr", and before "limit", if "limit" is non-NULL.  If there is no
  91   // such bit, returns "limit" if that is non-NULL, or else "endWord()".
  92   HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
  93                                      const HeapWord* limit = NULL) const;
  94   // Return the address corresponding to the next unmarked bit at or after
  95   // "addr", and before "limit", if "limit" is non-NULL.  If there is no
  96   // such bit, returns "limit" if that is non-NULL, or else "endWord()".
  97   HeapWord* getNextUnmarkedWordAddress(const HeapWord* addr,
  98                                        const HeapWord* limit = NULL) const;
  99 
 100   // conversion utilities
 101   HeapWord* offsetToHeapWord(size_t offset) const {
 102     return _bmStartWord + (offset << _shifter);
 103   }
 104   size_t heapWordToOffset(const HeapWord* addr) const {
 105     return pointer_delta(addr, _bmStartWord) >> _shifter;
 106   }
 107   int heapWordDiffToOffsetDiff(size_t diff) const;
 108 
 109   // The argument addr should be the start address of a valid object
 110   HeapWord* nextObject(HeapWord* addr) {
 111     oop obj = (oop) addr;
 112     HeapWord* res =  addr + obj->size();
 113     assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
 114     return res;
 115   }
 116 
 117   void print_on_error(outputStream* st, const char* prefix) const;
 118 
 119   // debugging
 120   NOT_PRODUCT(bool covers(MemRegion rs) const;)
 121 };
 122 
 123 class CMBitMapMappingChangedListener : public G1MappingChangedListener {
 124  private:
 125   CMBitMap* _bm;
 126  public:
 127   CMBitMapMappingChangedListener() : _bm(NULL) {}
 128 
 129   void set_bitmap(CMBitMap* bm) { _bm = bm; }
 130 
 131   virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
 132 };
 133 
 134 class CMBitMap : public CMBitMapRO {
 135  private:
 136   CMBitMapMappingChangedListener _listener;
 137 
 138  public:
 139   static size_t compute_size(size_t heap_size);
 140   // Returns the amount of bytes on the heap between two marks in the bitmap.
 141   static size_t mark_distance();
 142 
 143   CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
 144 
 145   // Initializes the underlying BitMap to cover the given area.
 146   void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
 147 
 148   // Write marks.
 149   inline void mark(HeapWord* addr);
 150   inline void clear(HeapWord* addr);
 151   inline bool parMark(HeapWord* addr);
 152   inline bool parClear(HeapWord* addr);
 153 
 154   void markRange(MemRegion mr);
 155   void clearRange(MemRegion mr);
 156 
 157   // Starting at the bit corresponding to "addr" (inclusive), find the next
 158   // "1" bit, if any.  This bit starts some run of consecutive "1"'s; find
 159   // the end of this run (stopping at "end_addr").  Return the MemRegion
 160   // covering from the start of the region corresponding to the first bit
 161   // of the run to the end of the region corresponding to the last bit of
 162   // the run.  If there is no "1" bit at or after "addr", return an empty
 163   // MemRegion.
 164   MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
 165 
 166   // Clear the whole mark bitmap.
 167   void clearAll();
 168 };
 169 
 170 // Represents a marking stack used by ConcurrentMarking in the G1 collector.
 171 class CMMarkStack VALUE_OBJ_CLASS_SPEC {
 172   VirtualSpace _virtual_space;   // Underlying backing store for actual stack
 173   ConcurrentMark* _cm;
 174   oop* _base;        // bottom of stack
 175   jint _index;       // one more than last occupied index
 176   jint _capacity;    // max #elements
 177   jint _saved_index; // value of _index saved at start of GC
 178   NOT_PRODUCT(jint _max_depth;)   // max depth plumbed during run
 179 
 180   bool  _overflow;
 181   bool  _should_expand;
 182   DEBUG_ONLY(bool _drain_in_progress;)
 183   DEBUG_ONLY(bool _drain_in_progress_yields;)
 184 
 185  public:
 186   CMMarkStack() { }
 187   CMMarkStack(ConcurrentMark* cm);
 188   ~CMMarkStack();
 189 
 190 #ifndef PRODUCT
 191   jint max_depth() const {
 192     return _max_depth;
 193   }
 194 #endif
 195 
 196   bool allocate(size_t capacity);
 197 
 198   oop pop() {
 199     if (!isEmpty()) {
 200       return _base[--_index] ;
 201     }
 202     return NULL;
 203   }
 204 
 205   // If overflow happens, don't do the push, and record the overflow.
 206   // *Requires* that "ptr" is already marked.
 207   void push(oop ptr) {
 208     if (isFull()) {
 209       // Record overflow.
 210       _overflow = true;
 211       return;
 212     } else {
 213       _base[_index++] = ptr;
 214       NOT_PRODUCT(_max_depth = MAX2(_max_depth, _index));
 215     }
 216   }
 217   // Non-block impl.  Note: concurrency is allowed only with other
 218   // "par_push" operations, not with "pop" or "drain".  We would need
 219   // parallel versions of them if such concurrency was desired.
 220   void par_push(oop ptr);
 221 
 222   // Pushes the first "n" elements of "ptr_arr" on the stack.
 223   // Non-block impl.  Note: concurrency is allowed only with other
 224   // "par_adjoin_arr" or "push" operations, not with "pop" or "drain".
 225   void par_adjoin_arr(oop* ptr_arr, int n);
 226 
 227   // Pushes the first "n" elements of "ptr_arr" on the stack.
 228   // Locking impl: concurrency is allowed only with
 229   // "par_push_arr" and/or "par_pop_arr" operations, which use the same
 230   // locking strategy.
 231   void par_push_arr(oop* ptr_arr, int n);
 232 
 233   // If returns false, the array was empty.  Otherwise, removes up to "max"
 234   // elements from the stack, and transfers them to "ptr_arr" in an
 235   // unspecified order.  The actual number transferred is given in "n" ("n
 236   // == 0" is deliberately redundant with the return value.)  Locking impl:
 237   // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
 238   // operations, which use the same locking strategy.
 239   bool par_pop_arr(oop* ptr_arr, int max, int* n);
 240 
 241   // Drain the mark stack, applying the given closure to all fields of
 242   // objects on the stack.  (That is, continue until the stack is empty,
 243   // even if closure applications add entries to the stack.)  The "bm"
 244   // argument, if non-null, may be used to verify that only marked objects
 245   // are on the mark stack.  If "yield_after" is "true", then the
 246   // concurrent marker performing the drain offers to yield after
 247   // processing each object.  If a yield occurs, stops the drain operation
 248   // and returns false.  Otherwise, returns true.
 249   template<class OopClosureClass>
 250   bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
 251 
 252   bool isEmpty()    { return _index == 0; }
 253   bool isFull()     { return _index == _capacity; }
 254   int  maxElems()   { return _capacity; }
 255 
 256   bool overflow() { return _overflow; }
 257   void clear_overflow() { _overflow = false; }
 258 
 259   bool should_expand() const { return _should_expand; }
 260   void set_should_expand();
 261 
 262   // Expand the stack, typically in response to an overflow condition
 263   void expand();
 264 
 265   int  size() { return _index; }
 266 
 267   void setEmpty()   { _index = 0; clear_overflow(); }
 268 
 269   // Record the current index.
 270   void note_start_of_gc();
 271 
 272   // Make sure that we have not added any entries to the stack during GC.
 273   void note_end_of_gc();
 274 
 275   // iterate over the oops in the mark stack, up to the bound recorded via
 276   // the call above.
 277   void oops_do(OopClosure* f);
 278 };
 279 
 280 class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
 281 private:
 282 #ifndef PRODUCT
 283   uintx _num_remaining;
 284   bool _force;
 285 #endif // !defined(PRODUCT)
 286 
 287 public:
 288   void init() PRODUCT_RETURN;
 289   void update() PRODUCT_RETURN;
 290   bool should_force() PRODUCT_RETURN_( return false; );
 291 };
 292 
 293 // this will enable a variety of different statistics per GC task
 294 #define _MARKING_STATS_       0
 295 // this will enable the higher verbose levels
 296 #define _MARKING_VERBOSE_     0
 297 
 298 #if _MARKING_STATS_
 299 #define statsOnly(statement)  \
 300 do {                          \
 301   statement ;                 \
 302 } while (0)
 303 #else // _MARKING_STATS_
 304 #define statsOnly(statement)  \
 305 do {                          \
 306 } while (0)
 307 #endif // _MARKING_STATS_
 308 
 309 typedef enum {
 310   no_verbose  = 0,   // verbose turned off
 311   stats_verbose,     // only prints stats at the end of marking
 312   low_verbose,       // low verbose, mostly per region and per major event
 313   medium_verbose,    // a bit more detailed than low
 314   high_verbose       // per object verbose
 315 } CMVerboseLevel;
 316 
 317 class YoungList;
 318 
 319 // Root Regions are regions that are not empty at the beginning of a
 320 // marking cycle and which we might collect during an evacuation pause
 321 // while the cycle is active. Given that, during evacuation pauses, we
 322 // do not copy objects that are explicitly marked, what we have to do
 323 // for the root regions is to scan them and mark all objects reachable
 324 // from them. According to the SATB assumptions, we only need to visit
 325 // each object once during marking. So, as long as we finish this scan
 326 // before the next evacuation pause, we can copy the objects from the
 327 // root regions without having to mark them or do anything else to them.
 328 //
 329 // Currently, we only support root region scanning once (at the start
 330 // of the marking cycle) and the root regions are all the survivor
 331 // regions populated during the initial-mark pause.
 332 class CMRootRegions VALUE_OBJ_CLASS_SPEC {
 333 private:
 334   YoungList*           _young_list;
 335   ConcurrentMark*      _cm;
 336 
 337   volatile bool        _scan_in_progress;
 338   volatile bool        _should_abort;
 339   HeapRegion* volatile _next_survivor;
 340 
 341 public:
 342   CMRootRegions();
 343   // We actually do most of the initialization in this method.
 344   void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
 345 
 346   // Reset the claiming / scanning of the root regions.
 347   void prepare_for_scan();
 348 
 349   // Forces get_next() to return NULL so that the iteration aborts early.
 350   void abort() { _should_abort = true; }
 351 
 352   // Return true if the CM thread are actively scanning root regions,
 353   // false otherwise.
 354   bool scan_in_progress() { return _scan_in_progress; }
 355 
 356   // Claim the next root region to scan atomically, or return NULL if
 357   // all have been claimed.
 358   HeapRegion* claim_next();
 359 
 360   // Flag that we're done with root region scanning and notify anyone
 361   // who's waiting on it. If aborted is false, assume that all regions
 362   // have been claimed.
 363   void scan_finished();
 364 
 365   // If CM threads are still scanning root regions, wait until they
 366   // are done. Return true if we had to wait, false otherwise.
 367   bool wait_until_scan_finished();
 368 };
 369 
 370 class ConcurrentMarkThread;
 371 
 372 class ConcurrentMark: public CHeapObj<mtGC> {
 373   friend class CMMarkStack;
 374   friend class ConcurrentMarkThread;
 375   friend class CMTask;
 376   friend class CMBitMapClosure;
 377   friend class CMGlobalObjectClosure;
 378   friend class CMRemarkTask;
 379   friend class CMConcurrentMarkingTask;
 380   friend class G1ParNoteEndTask;
 381   friend class CalcLiveObjectsClosure;
 382   friend class G1CMRefProcTaskProxy;
 383   friend class G1CMRefProcTaskExecutor;
 384   friend class G1CMKeepAliveAndDrainClosure;
 385   friend class G1CMDrainMarkingStackClosure;
 386 
 387 protected:
 388   ConcurrentMarkThread* _cmThread;   // The thread doing the work
 389   G1CollectedHeap*      _g1h;        // The heap
 390   uint                  _parallel_marking_threads; // The number of marking
 391                                                    // threads we're using
 392   uint                  _max_parallel_marking_threads; // Max number of marking
 393                                                        // threads we'll ever use
 394   double                _sleep_factor; // How much we have to sleep, with
 395                                        // respect to the work we just did, to
 396                                        // meet the marking overhead goal
 397   double                _marking_task_overhead; // Marking target overhead for
 398                                                 // a single task
 399 
 400   // Same as the two above, but for the cleanup task
 401   double                _cleanup_sleep_factor;
 402   double                _cleanup_task_overhead;
 403 
 404   FreeRegionList        _cleanup_list;
 405 
 406   // Concurrent marking support structures
 407   CMBitMap                _markBitMap1;
 408   CMBitMap                _markBitMap2;
 409   CMBitMapRO*             _prevMarkBitMap; // Completed mark bitmap
 410   CMBitMap*               _nextMarkBitMap; // Under-construction mark bitmap
 411 
 412   BitMap                  _region_bm;
 413   BitMap                  _card_bm;
 414 
 415   // Heap bounds
 416   HeapWord*               _heap_start;
 417   HeapWord*               _heap_end;
 418 
 419   // Root region tracking and claiming
 420   CMRootRegions           _root_regions;
 421 
 422   // For gray objects
 423   CMMarkStack             _markStack; // Grey objects behind global finger
 424   HeapWord* volatile      _finger;  // The global finger, region aligned,
 425                                     // always points to the end of the
 426                                     // last claimed region
 427 
 428   // Marking tasks
 429   uint                    _max_worker_id;// Maximum worker id
 430   uint                    _active_tasks; // Task num currently active
 431   CMTask**                _tasks;        // Task queue array (max_worker_id len)
 432   CMTaskQueueSet*         _task_queues;  // Task queue set
 433   ParallelTaskTerminator  _terminator;   // For termination
 434 
 435   // Two sync barriers that are used to synchronize tasks when an
 436   // overflow occurs. The algorithm is the following. All tasks enter
 437   // the first one to ensure that they have all stopped manipulating
 438   // the global data structures. After they exit it, they re-initialize
 439   // their data structures and task 0 re-initializes the global data
 440   // structures. Then, they enter the second sync barrier. This
 441   // ensure, that no task starts doing work before all data
 442   // structures (local and global) have been re-initialized. When they
 443   // exit it, they are free to start working again.
 444   WorkGangBarrierSync     _first_overflow_barrier_sync;
 445   WorkGangBarrierSync     _second_overflow_barrier_sync;
 446 
 447   // This is set by any task, when an overflow on the global data
 448   // structures is detected
 449   volatile bool           _has_overflown;
 450   // True: marking is concurrent, false: we're in remark
 451   volatile bool           _concurrent;
 452   // Set at the end of a Full GC so that marking aborts
 453   volatile bool           _has_aborted;
 454   GCId                    _aborted_gc_id;
 455 
 456   // Used when remark aborts due to an overflow to indicate that
 457   // another concurrent marking phase should start
 458   volatile bool           _restart_for_overflow;
 459 
 460   // This is true from the very start of concurrent marking until the
 461   // point when all the tasks complete their work. It is really used
 462   // to determine the points between the end of concurrent marking and
 463   // time of remark.
 464   volatile bool           _concurrent_marking_in_progress;
 465 
 466   // Verbose level
 467   CMVerboseLevel          _verbose_level;
 468 
 469   // All of these times are in ms
 470   NumberSeq _init_times;
 471   NumberSeq _remark_times;
 472   NumberSeq   _remark_mark_times;
 473   NumberSeq   _remark_weak_ref_times;
 474   NumberSeq _cleanup_times;
 475   double    _total_counting_time;
 476   double    _total_rs_scrub_time;
 477 
 478   double*   _accum_task_vtime;   // Accumulated task vtime
 479 
 480   FlexibleWorkGang* _parallel_workers;
 481 
 482   ForceOverflowSettings _force_overflow_conc;
 483   ForceOverflowSettings _force_overflow_stw;
 484 
 485   void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
 486   void weakRefsWork(bool clear_all_soft_refs);
 487 
 488   void swapMarkBitMaps();
 489 
 490   // It resets the global marking data structures, as well as the
 491   // task local ones; should be called during initial mark.
 492   void reset();
 493 
 494   // Resets all the marking data structures. Called when we have to restart
 495   // marking or when marking completes (via set_non_marking_state below).
 496   void reset_marking_state(bool clear_overflow = true);
 497 
 498   // We do this after we're done with marking so that the marking data
 499   // structures are initialized to a sensible and predictable state.
 500   void set_non_marking_state();
 501 
 502   // Called to indicate how many threads are currently active.
 503   void set_concurrency(uint active_tasks);
 504 
 505   // It should be called to indicate which phase we're in (concurrent
 506   // mark or remark) and how many threads are currently active.
 507   void set_concurrency_and_phase(uint active_tasks, bool concurrent);
 508 
 509   // Prints all gathered CM-related statistics
 510   void print_stats();
 511 
 512   bool cleanup_list_is_empty() {
 513     return _cleanup_list.is_empty();
 514   }
 515 
 516   // Accessor methods
 517   uint parallel_marking_threads() const     { return _parallel_marking_threads; }
 518   uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
 519   double sleep_factor()                     { return _sleep_factor; }
 520   double marking_task_overhead()            { return _marking_task_overhead;}
 521   double cleanup_sleep_factor()             { return _cleanup_sleep_factor; }
 522   double cleanup_task_overhead()            { return _cleanup_task_overhead;}
 523 
 524   HeapWord*               finger()          { return _finger;   }
 525   bool                    concurrent()      { return _concurrent; }
 526   uint                    active_tasks()    { return _active_tasks; }
 527   ParallelTaskTerminator* terminator()      { return &_terminator; }
 528 
 529   // It claims the next available region to be scanned by a marking
 530   // task/thread. It might return NULL if the next region is empty or
 531   // we have run out of regions. In the latter case, out_of_regions()
 532   // determines whether we've really run out of regions or the task
 533   // should call claim_region() again. This might seem a bit
 534   // awkward. Originally, the code was written so that claim_region()
 535   // either successfully returned with a non-empty region or there
 536   // were no more regions to be claimed. The problem with this was
 537   // that, in certain circumstances, it iterated over large chunks of
 538   // the heap finding only empty regions and, while it was working, it
 539   // was preventing the calling task to call its regular clock
 540   // method. So, this way, each task will spend very little time in
 541   // claim_region() and is allowed to call the regular clock method
 542   // frequently.
 543   HeapRegion* claim_region(uint worker_id);
 544 
 545   // It determines whether we've run out of regions to scan. Note that
 546   // the finger can point past the heap end in case the heap was expanded
 547   // to satisfy an allocation without doing a GC. This is fine, because all
 548   // objects in those regions will be considered live anyway because of
 549   // SATB guarantees (i.e. their TAMS will be equal to bottom).
 550   bool        out_of_regions() { return _finger >= _heap_end; }
 551 
 552   // Returns the task with the given id
 553   CMTask* task(int id) {
 554     assert(0 <= id && id < (int) _active_tasks,
 555            "task id not within active bounds");
 556     return _tasks[id];
 557   }
 558 
 559   // Returns the task queue with the given id
 560   CMTaskQueue* task_queue(int id) {
 561     assert(0 <= id && id < (int) _active_tasks,
 562            "task queue id not within active bounds");
 563     return (CMTaskQueue*) _task_queues->queue(id);
 564   }
 565 
 566   // Returns the task queue set
 567   CMTaskQueueSet* task_queues()  { return _task_queues; }
 568 
 569   // Access / manipulation of the overflow flag which is set to
 570   // indicate that the global stack has overflown
 571   bool has_overflown()           { return _has_overflown; }
 572   void set_has_overflown()       { _has_overflown = true; }
 573   void clear_has_overflown()     { _has_overflown = false; }
 574   bool restart_for_overflow()    { return _restart_for_overflow; }
 575 
 576   // Methods to enter the two overflow sync barriers
 577   void enter_first_sync_barrier(uint worker_id);
 578   void enter_second_sync_barrier(uint worker_id);
 579 
 580   ForceOverflowSettings* force_overflow_conc() {
 581     return &_force_overflow_conc;
 582   }
 583 
 584   ForceOverflowSettings* force_overflow_stw() {
 585     return &_force_overflow_stw;
 586   }
 587 
 588   ForceOverflowSettings* force_overflow() {
 589     if (concurrent()) {
 590       return force_overflow_conc();
 591     } else {
 592       return force_overflow_stw();
 593     }
 594   }
 595 
 596   // Live Data Counting data structures...
 597   // These data structures are initialized at the start of
 598   // marking. They are written to while marking is active.
 599   // They are aggregated during remark; the aggregated values
 600   // are then used to populate the _region_bm, _card_bm, and
 601   // the total live bytes, which are then subsequently updated
 602   // during cleanup.
 603 
 604   // An array of bitmaps (one bit map per task). Each bitmap
 605   // is used to record the cards spanned by the live objects
 606   // marked by that task/worker.
 607   BitMap*  _count_card_bitmaps;
 608 
 609   // Used to record the number of marked live bytes
 610   // (for each region, by worker thread).
 611   size_t** _count_marked_bytes;
 612 
 613   // Card index of the bottom of the G1 heap. Used for biasing indices into
 614   // the card bitmaps.
 615   intptr_t _heap_bottom_card_num;
 616 
 617   // Set to true when initialization is complete
 618   bool _completed_initialization;
 619 
 620 public:
 621   // Manipulation of the global mark stack.
 622   // Notice that the first mark_stack_push is CAS-based, whereas the
 623   // two below are Mutex-based. This is OK since the first one is only
 624   // called during evacuation pauses and doesn't compete with the
 625   // other two (which are called by the marking tasks during
 626   // concurrent marking or remark).
 627   bool mark_stack_push(oop p) {
 628     _markStack.par_push(p);
 629     if (_markStack.overflow()) {
 630       set_has_overflown();
 631       return false;
 632     }
 633     return true;
 634   }
 635   bool mark_stack_push(oop* arr, int n) {
 636     _markStack.par_push_arr(arr, n);
 637     if (_markStack.overflow()) {
 638       set_has_overflown();
 639       return false;
 640     }
 641     return true;
 642   }
 643   void mark_stack_pop(oop* arr, int max, int* n) {
 644     _markStack.par_pop_arr(arr, max, n);
 645   }
 646   size_t mark_stack_size()                { return _markStack.size(); }
 647   size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
 648   bool mark_stack_overflow()              { return _markStack.overflow(); }
 649   bool mark_stack_empty()                 { return _markStack.isEmpty(); }
 650 
 651   CMRootRegions* root_regions() { return &_root_regions; }
 652 
 653   bool concurrent_marking_in_progress() {
 654     return _concurrent_marking_in_progress;
 655   }
 656   void set_concurrent_marking_in_progress() {
 657     _concurrent_marking_in_progress = true;
 658   }
 659   void clear_concurrent_marking_in_progress() {
 660     _concurrent_marking_in_progress = false;
 661   }
 662 
 663   void update_accum_task_vtime(int i, double vtime) {
 664     _accum_task_vtime[i] += vtime;
 665   }
 666 
 667   double all_task_accum_vtime() {
 668     double ret = 0.0;
 669     for (uint i = 0; i < _max_worker_id; ++i)
 670       ret += _accum_task_vtime[i];
 671     return ret;
 672   }
 673 
 674   // Attempts to steal an object from the task queues of other tasks
 675   bool try_stealing(uint worker_id, int* hash_seed, oop& obj) {
 676     return _task_queues->steal(worker_id, hash_seed, obj);
 677   }
 678 
 679   ConcurrentMark(G1CollectedHeap* g1h,
 680                  G1RegionToSpaceMapper* prev_bitmap_storage,
 681                  G1RegionToSpaceMapper* next_bitmap_storage);
 682   ~ConcurrentMark();
 683 
 684   ConcurrentMarkThread* cmThread() { return _cmThread; }
 685 
 686   CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
 687   CMBitMap*   nextMarkBitMap() const { return _nextMarkBitMap; }
 688 
 689   // Returns the number of GC threads to be used in a concurrent
 690   // phase based on the number of GC threads being used in a STW
 691   // phase.
 692   uint scale_parallel_threads(uint n_par_threads);
 693 
 694   // Calculates the number of GC threads to be used in a concurrent phase.
 695   uint calc_parallel_marking_threads();
 696 
 697   // The following three are interaction between CM and
 698   // G1CollectedHeap
 699 
 700   // This notifies CM that a root during initial-mark needs to be
 701   // grayed. It is MT-safe. word_size is the size of the object in
 702   // words. It is passed explicitly as sometimes we cannot calculate
 703   // it from the given object because it might be in an inconsistent
 704   // state (e.g., in to-space and being copied). So the caller is
 705   // responsible for dealing with this issue (e.g., get the size from
 706   // the from-space image when the to-space image might be
 707   // inconsistent) and always passing the size. hr is the region that
 708   // contains the object and it's passed optionally from callers who
 709   // might already have it (no point in recalculating it).
 710   inline void grayRoot(oop obj,
 711                        size_t word_size,
 712                        uint worker_id,
 713                        HeapRegion* hr = NULL);
 714 
 715   // It iterates over the heap and for each object it comes across it
 716   // will dump the contents of its reference fields, as well as
 717   // liveness information for the object and its referents. The dump
 718   // will be written to a file with the following name:
 719   // G1PrintReachableBaseFile + "." + str.
 720   // vo decides whether the prev (vo == UsePrevMarking), the next
 721   // (vo == UseNextMarking) marking information, or the mark word
 722   // (vo == UseMarkWord) will be used to determine the liveness of
 723   // each object / referent.
 724   // If all is true, all objects in the heap will be dumped, otherwise
 725   // only the live ones. In the dump the following symbols / breviations
 726   // are used:
 727   //   M : an explicitly live object (its bitmap bit is set)
 728   //   > : an implicitly live object (over tams)
 729   //   O : an object outside the G1 heap (typically: in the perm gen)
 730   //   NOT : a reference field whose referent is not live
 731   //   AND MARKED : indicates that an object is both explicitly and
 732   //   implicitly live (it should be one or the other, not both)
 733   void print_reachable(const char* str,
 734                        VerifyOption vo,
 735                        bool all) PRODUCT_RETURN;
 736 
 737   // Clear the next marking bitmap (will be called concurrently).
 738   void clearNextBitmap();
 739 
 740   // Return whether the next mark bitmap has no marks set. To be used for assertions
 741   // only. Will not yield to pause requests.
 742   bool nextMarkBitmapIsClear();
 743 
 744   // These two do the work that needs to be done before and after the
 745   // initial root checkpoint. Since this checkpoint can be done at two
 746   // different points (i.e. an explicit pause or piggy-backed on a
 747   // young collection), then it's nice to be able to easily share the
 748   // pre/post code. It might be the case that we can put everything in
 749   // the post method. TP
 750   void checkpointRootsInitialPre();
 751   void checkpointRootsInitialPost();
 752 
 753   // Scan all the root regions and mark everything reachable from
 754   // them.
 755   void scanRootRegions();
 756 
 757   // Scan a single root region and mark everything reachable from it.
 758   void scanRootRegion(HeapRegion* hr, uint worker_id);
 759 
 760   // Do concurrent phase of marking, to a tentative transitive closure.
 761   void markFromRoots();
 762 
 763   void checkpointRootsFinal(bool clear_all_soft_refs);
 764   void checkpointRootsFinalWork();
 765   void cleanup();
 766   void completeCleanup();
 767 
 768   // Mark in the previous bitmap.  NB: this is usually read-only, so use
 769   // this carefully!
 770   inline void markPrev(oop p);
 771 
 772   // Clears marks for all objects in the given range, for the prev or
 773   // next bitmaps.  NB: the previous bitmap is usually
 774   // read-only, so use this carefully!
 775   void clearRangePrevBitmap(MemRegion mr);
 776   void clearRangeNextBitmap(MemRegion mr);
 777 
 778   // Notify data structures that a GC has started.
 779   void note_start_of_gc() {
 780     _markStack.note_start_of_gc();
 781   }
 782 
 783   // Notify data structures that a GC is finished.
 784   void note_end_of_gc() {
 785     _markStack.note_end_of_gc();
 786   }
 787 
 788   // Verify that there are no CSet oops on the stacks (taskqueues /
 789   // global mark stack), enqueued SATB buffers, per-thread SATB
 790   // buffers, and fingers (global / per-task). The boolean parameters
 791   // decide which of the above data structures to verify. If marking
 792   // is not in progress, it's a no-op.
 793   void verify_no_cset_oops(bool verify_stacks,
 794                            bool verify_enqueued_buffers,
 795                            bool verify_thread_buffers,
 796                            bool verify_fingers) PRODUCT_RETURN;
 797 
 798   bool isPrevMarked(oop p) const {
 799     assert(p != NULL && p->is_oop(), "expected an oop");
 800     HeapWord* addr = (HeapWord*)p;
 801     assert(addr >= _prevMarkBitMap->startWord() ||
 802            addr < _prevMarkBitMap->endWord(), "in a region");
 803 
 804     return _prevMarkBitMap->isMarked(addr);
 805   }
 806 
 807   inline bool do_yield_check(uint worker_i = 0);
 808 
 809   // Called to abort the marking cycle after a Full GC takes place.
 810   void abort();
 811 
 812   bool has_aborted()      { return _has_aborted; }
 813 
 814   const GCId& concurrent_gc_id();
 815 
 816   // This prints the global/local fingers. It is used for debugging.
 817   NOT_PRODUCT(void print_finger();)
 818 
 819   void print_summary_info();
 820 
 821   void print_worker_threads_on(outputStream* st) const;
 822 
 823   void print_on_error(outputStream* st) const;
 824 
 825   // The following indicate whether a given verbose level has been
 826   // set. Notice that anything above stats is conditional to
 827   // _MARKING_VERBOSE_ having been set to 1
 828   bool verbose_stats() {
 829     return _verbose_level >= stats_verbose;
 830   }
 831   bool verbose_low() {
 832     return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
 833   }
 834   bool verbose_medium() {
 835     return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
 836   }
 837   bool verbose_high() {
 838     return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
 839   }
 840 
 841   // Liveness counting
 842 
 843   // Utility routine to set an exclusive range of cards on the given
 844   // card liveness bitmap
 845   inline void set_card_bitmap_range(BitMap* card_bm,
 846                                     BitMap::idx_t start_idx,
 847                                     BitMap::idx_t end_idx,
 848                                     bool is_par);
 849 
 850   // Returns the card number of the bottom of the G1 heap.
 851   // Used in biasing indices into accounting card bitmaps.
 852   intptr_t heap_bottom_card_num() const {
 853     return _heap_bottom_card_num;
 854   }
 855 
 856   // Returns the card bitmap for a given task or worker id.
 857   BitMap* count_card_bitmap_for(uint worker_id) {
 858     assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
 859     assert(_count_card_bitmaps != NULL, "uninitialized");
 860     BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
 861     assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
 862     return task_card_bm;
 863   }
 864 
 865   // Returns the array containing the marked bytes for each region,
 866   // for the given worker or task id.
 867   size_t* count_marked_bytes_array_for(uint worker_id) {
 868     assert(0 <= worker_id && worker_id < _max_worker_id, "oob");
 869     assert(_count_marked_bytes != NULL, "uninitialized");
 870     size_t* marked_bytes_array = _count_marked_bytes[worker_id];
 871     assert(marked_bytes_array != NULL, "uninitialized");
 872     return marked_bytes_array;
 873   }
 874 
 875   // Returns the index in the liveness accounting card table bitmap
 876   // for the given address
 877   inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
 878 
 879   // Counts the size of the given memory region in the the given
 880   // marked_bytes array slot for the given HeapRegion.
 881   // Sets the bits in the given card bitmap that are associated with the
 882   // cards that are spanned by the memory region.
 883   inline void count_region(MemRegion mr,
 884                            HeapRegion* hr,
 885                            size_t* marked_bytes_array,
 886                            BitMap* task_card_bm);
 887 
 888   // Counts the given memory region in the task/worker counting
 889   // data structures for the given worker id.
 890   inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
 891 
 892   // Counts the given object in the given task/worker counting
 893   // data structures.
 894   inline void count_object(oop obj,
 895                            HeapRegion* hr,
 896                            size_t* marked_bytes_array,
 897                            BitMap* task_card_bm);
 898 
 899   // Attempts to mark the given object and, if successful, counts
 900   // the object in the given task/worker counting structures.
 901   inline bool par_mark_and_count(oop obj,
 902                                  HeapRegion* hr,
 903                                  size_t* marked_bytes_array,
 904                                  BitMap* task_card_bm);
 905 
 906   // Attempts to mark the given object and, if successful, counts
 907   // the object in the task/worker counting structures for the
 908   // given worker id.
 909   inline bool par_mark_and_count(oop obj,
 910                                  size_t word_size,
 911                                  HeapRegion* hr,
 912                                  uint worker_id);
 913 
 914   // Returns true if initialization was successfully completed.
 915   bool completed_initialization() const {
 916     return _completed_initialization;
 917   }
 918 
 919 protected:
 920   // Clear all the per-task bitmaps and arrays used to store the
 921   // counting data.
 922   void clear_all_count_data();
 923 
 924   // Aggregates the counting data for each worker/task
 925   // that was constructed while marking. Also sets
 926   // the amount of marked bytes for each region and
 927   // the top at concurrent mark count.
 928   void aggregate_count_data();
 929 
 930   // Verification routine
 931   void verify_count_data();
 932 };
 933 
 934 // A class representing a marking task.
 935 class CMTask : public TerminatorTerminator {
 936 private:
 937   enum PrivateConstants {
 938     // the regular clock call is called once the scanned words reaches
 939     // this limit
 940     words_scanned_period          = 12*1024,
 941     // the regular clock call is called once the number of visited
 942     // references reaches this limit
 943     refs_reached_period           = 384,
 944     // initial value for the hash seed, used in the work stealing code
 945     init_hash_seed                = 17,
 946     // how many entries will be transferred between global stack and
 947     // local queues
 948     global_stack_transfer_size    = 16
 949   };
 950 
 951   uint                        _worker_id;
 952   G1CollectedHeap*            _g1h;
 953   ConcurrentMark*             _cm;
 954   CMBitMap*                   _nextMarkBitMap;
 955   // the task queue of this task
 956   CMTaskQueue*                _task_queue;
 957 private:
 958   // the task queue set---needed for stealing
 959   CMTaskQueueSet*             _task_queues;
 960   // indicates whether the task has been claimed---this is only  for
 961   // debugging purposes
 962   bool                        _claimed;
 963 
 964   // number of calls to this task
 965   int                         _calls;
 966 
 967   // when the virtual timer reaches this time, the marking step should
 968   // exit
 969   double                      _time_target_ms;
 970   // the start time of the current marking step
 971   double                      _start_time_ms;
 972 
 973   // the oop closure used for iterations over oops
 974   G1CMOopClosure*             _cm_oop_closure;
 975 
 976   // the region this task is scanning, NULL if we're not scanning any
 977   HeapRegion*                 _curr_region;
 978   // the local finger of this task, NULL if we're not scanning a region
 979   HeapWord*                   _finger;
 980   // limit of the region this task is scanning, NULL if we're not scanning one
 981   HeapWord*                   _region_limit;
 982 
 983   // the number of words this task has scanned
 984   size_t                      _words_scanned;
 985   // When _words_scanned reaches this limit, the regular clock is
 986   // called. Notice that this might be decreased under certain
 987   // circumstances (i.e. when we believe that we did an expensive
 988   // operation).
 989   size_t                      _words_scanned_limit;
 990   // the initial value of _words_scanned_limit (i.e. what it was
 991   // before it was decreased).
 992   size_t                      _real_words_scanned_limit;
 993 
 994   // the number of references this task has visited
 995   size_t                      _refs_reached;
 996   // When _refs_reached reaches this limit, the regular clock is
 997   // called. Notice this this might be decreased under certain
 998   // circumstances (i.e. when we believe that we did an expensive
 999   // operation).
1000   size_t                      _refs_reached_limit;
1001   // the initial value of _refs_reached_limit (i.e. what it was before
1002   // it was decreased).
1003   size_t                      _real_refs_reached_limit;
1004 
1005   // used by the work stealing stuff
1006   int                         _hash_seed;
1007   // if this is true, then the task has aborted for some reason
1008   bool                        _has_aborted;
1009   // set when the task aborts because it has met its time quota
1010   bool                        _has_timed_out;
1011   // true when we're draining SATB buffers; this avoids the task
1012   // aborting due to SATB buffers being available (as we're already
1013   // dealing with them)
1014   bool                        _draining_satb_buffers;
1015 
1016   // number sequence of past step times
1017   NumberSeq                   _step_times_ms;
1018   // elapsed time of this task
1019   double                      _elapsed_time_ms;
1020   // termination time of this task
1021   double                      _termination_time_ms;
1022   // when this task got into the termination protocol
1023   double                      _termination_start_time_ms;
1024 
1025   // true when the task is during a concurrent phase, false when it is
1026   // in the remark phase (so, in the latter case, we do not have to
1027   // check all the things that we have to check during the concurrent
1028   // phase, i.e. SATB buffer availability...)
1029   bool                        _concurrent;
1030 
1031   TruncatedSeq                _marking_step_diffs_ms;
1032 
1033   // Counting data structures. Embedding the task's marked_bytes_array
1034   // and card bitmap into the actual task saves having to go through
1035   // the ConcurrentMark object.
1036   size_t*                     _marked_bytes_array;
1037   BitMap*                     _card_bm;
1038 
1039   // LOTS of statistics related with this task
1040 #if _MARKING_STATS_
1041   NumberSeq                   _all_clock_intervals_ms;
1042   double                      _interval_start_time_ms;
1043 
1044   int                         _aborted;
1045   int                         _aborted_overflow;
1046   int                         _aborted_cm_aborted;
1047   int                         _aborted_yield;
1048   int                         _aborted_timed_out;
1049   int                         _aborted_satb;
1050   int                         _aborted_termination;
1051 
1052   int                         _steal_attempts;
1053   int                         _steals;
1054 
1055   int                         _clock_due_to_marking;
1056   int                         _clock_due_to_scanning;
1057 
1058   int                         _local_pushes;
1059   int                         _local_pops;
1060   int                         _local_max_size;
1061   int                         _objs_scanned;
1062 
1063   int                         _global_pushes;
1064   int                         _global_pops;
1065   int                         _global_max_size;
1066 
1067   int                         _global_transfers_to;
1068   int                         _global_transfers_from;
1069 
1070   int                         _regions_claimed;
1071   int                         _objs_found_on_bitmap;
1072 
1073   int                         _satb_buffers_processed;
1074 #endif // _MARKING_STATS_
1075 
1076   // it updates the local fields after this task has claimed
1077   // a new region to scan
1078   void setup_for_region(HeapRegion* hr);
1079   // it brings up-to-date the limit of the region
1080   void update_region_limit();
1081 
1082   // called when either the words scanned or the refs visited limit
1083   // has been reached
1084   void reached_limit();
1085   // recalculates the words scanned and refs visited limits
1086   void recalculate_limits();
1087   // decreases the words scanned and refs visited limits when we reach
1088   // an expensive operation
1089   void decrease_limits();
1090   // it checks whether the words scanned or refs visited reached their
1091   // respective limit and calls reached_limit() if they have
1092   void check_limits() {
1093     if (_words_scanned >= _words_scanned_limit ||
1094         _refs_reached >= _refs_reached_limit) {
1095       reached_limit();
1096     }
1097   }
1098   // this is supposed to be called regularly during a marking step as
1099   // it checks a bunch of conditions that might cause the marking step
1100   // to abort
1101   void regular_clock_call();
1102   bool concurrent() { return _concurrent; }
1103 
1104 public:
1105   // It resets the task; it should be called right at the beginning of
1106   // a marking phase.
1107   void reset(CMBitMap* _nextMarkBitMap);
1108   // it clears all the fields that correspond to a claimed region.
1109   void clear_region_fields();
1110 
1111   void set_concurrent(bool concurrent) { _concurrent = concurrent; }
1112 
1113   // The main method of this class which performs a marking step
1114   // trying not to exceed the given duration. However, it might exit
1115   // prematurely, according to some conditions (i.e. SATB buffers are
1116   // available for processing).
1117   void do_marking_step(double target_ms,
1118                        bool do_termination,
1119                        bool is_serial);
1120 
1121   // These two calls start and stop the timer
1122   void record_start_time() {
1123     _elapsed_time_ms = os::elapsedTime() * 1000.0;
1124   }
1125   void record_end_time() {
1126     _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
1127   }
1128 
1129   // returns the worker ID associated with this task.
1130   uint worker_id() { return _worker_id; }
1131 
1132   // From TerminatorTerminator. It determines whether this task should
1133   // exit the termination protocol after it's entered it.
1134   virtual bool should_exit_termination();
1135 
1136   // Resets the local region fields after a task has finished scanning a
1137   // region; or when they have become stale as a result of the region
1138   // being evacuated.
1139   void giveup_current_region();
1140 
1141   HeapWord* finger()            { return _finger; }
1142 
1143   bool has_aborted()            { return _has_aborted; }
1144   void set_has_aborted()        { _has_aborted = true; }
1145   void clear_has_aborted()      { _has_aborted = false; }
1146   bool has_timed_out()          { return _has_timed_out; }
1147   bool claimed()                { return _claimed; }
1148 
1149   void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
1150 
1151   // It grays the object by marking it and, if necessary, pushing it
1152   // on the local queue
1153   inline void deal_with_reference(oop obj);
1154 
1155   // It scans an object and visits its children.
1156   void scan_object(oop obj);
1157 
1158   // It pushes an object on the local queue.
1159   inline void push(oop obj);
1160 
1161   // These two move entries to/from the global stack.
1162   void move_entries_to_global_stack();
1163   void get_entries_from_global_stack();
1164 
1165   // It pops and scans objects from the local queue. If partially is
1166   // true, then it stops when the queue size is of a given limit. If
1167   // partially is false, then it stops when the queue is empty.
1168   void drain_local_queue(bool partially);
1169   // It moves entries from the global stack to the local queue and
1170   // drains the local queue. If partially is true, then it stops when
1171   // both the global stack and the local queue reach a given size. If
1172   // partially if false, it tries to empty them totally.
1173   void drain_global_stack(bool partially);
1174   // It keeps picking SATB buffers and processing them until no SATB
1175   // buffers are available.
1176   void drain_satb_buffers();
1177 
1178   // moves the local finger to a new location
1179   inline void move_finger_to(HeapWord* new_finger) {
1180     assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
1181     _finger = new_finger;
1182   }
1183 
1184   CMTask(uint worker_id,
1185          ConcurrentMark *cm,
1186          size_t* marked_bytes,
1187          BitMap* card_bm,
1188          CMTaskQueue* task_queue,
1189          CMTaskQueueSet* task_queues);
1190 
1191   // it prints statistics associated with this task
1192   void print_stats();
1193 
1194 #if _MARKING_STATS_
1195   void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
1196 #endif // _MARKING_STATS_
1197 };
1198 
1199 // Class that's used to to print out per-region liveness
1200 // information. It's currently used at the end of marking and also
1201 // after we sort the old regions at the end of the cleanup operation.
1202 class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
1203 private:
1204   outputStream* _out;
1205 
1206   // Accumulators for these values.
1207   size_t _total_used_bytes;
1208   size_t _total_capacity_bytes;
1209   size_t _total_prev_live_bytes;
1210   size_t _total_next_live_bytes;
1211 
1212   // These are set up when we come across a "stars humongous" region
1213   // (as this is where most of this information is stored, not in the
1214   // subsequent "continues humongous" regions). After that, for every
1215   // region in a given humongous region series we deduce the right
1216   // values for it by simply subtracting the appropriate amount from
1217   // these fields. All these values should reach 0 after we've visited
1218   // the last region in the series.
1219   size_t _hum_used_bytes;
1220   size_t _hum_capacity_bytes;
1221   size_t _hum_prev_live_bytes;
1222   size_t _hum_next_live_bytes;
1223 
1224   // Accumulator for the remembered set size
1225   size_t _total_remset_bytes;
1226 
1227   // Accumulator for strong code roots memory size
1228   size_t _total_strong_code_roots_bytes;
1229 
1230   static double perc(size_t val, size_t total) {
1231     if (total == 0) {
1232       return 0.0;
1233     } else {
1234       return 100.0 * ((double) val / (double) total);
1235     }
1236   }
1237 
1238   static double bytes_to_mb(size_t val) {
1239     return (double) val / (double) M;
1240   }
1241 
1242   // See the .cpp file.
1243   size_t get_hum_bytes(size_t* hum_bytes);
1244   void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
1245                      size_t* prev_live_bytes, size_t* next_live_bytes);
1246 
1247 public:
1248   // The header and footer are printed in the constructor and
1249   // destructor respectively.
1250   G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
1251   virtual bool doHeapRegion(HeapRegion* r);
1252   ~G1PrintRegionLivenessInfoClosure();
1253 };
1254 
1255 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_CONCURRENTMARK_HPP